Safe Days Calculator

9 min read

Safe days calculator helps you to find out the safe days in your menstrual cycle, that you can have sexual intercourse without the fear of getting pregnant. It just requires you to remember the starting date of your last period, and your longest and shortest menstrual cycle.

Once you have done this, you can easily calculate the safe and unsafe days of your menstrual cycle. If your menstrual cycle every month lies within (26 to 32 days), then you can use this calculator and know the safe days.

First day of your last menstrual period (LMP)
Shortest Cycle Length
Longest Cycle Length

How to Calculate the Longest & Shortest Menstrual Cycle?

You just need to count the number of days between the first days of your consecutive periods for six months. The month with more number of days is your longest menstrual cycle. And the month with the least number of days is your shortest menstrual cycle.

How to Calculate the Safe and Unsafe Days?

Note down the shortest menstrual cycle from the last six months, and subtract 18 days from the total number of days of shortest cycle.
The number of days that you get after subtracting 18 days, count that number of days from the first day of your last period and mark it as X. X is the first day of the fertile period which is unsafe period.
Next, note down the longest menstrual cycle from the last six months, and subtract 10 days from the total number of days of longest cycle.
The number of days you get after subtracting 10 days, count that number of days from the first day of your last period and mark it as Y. The days after Y is the safe period.
So, the days between X and Y are unsafe days to have sex, as there are chances of getting pregnant. All other days apart from these are considered as safe days.


The 28 days of the regular menstrual cycle, are divided into various phases to calculate ovulation, safe periods to have sex, and fertile periods. This can help in the proper planning for whether they want to have a successful pregnancy or not. Having sex during the safe period is also a natural method of contraception to avoid pregnancy, without the help of any physical contraceptive aids or pills. It is important to calculate the safe periods if not planning for a pregnancy.

What Is the Menstrual Cycle?
The changes in the female reproductive organ to get it ready for pregnancy every month is called the menstrual cycle. These changes result from the increase and decrease in the levels of female hormones estrogen and progesterone in the body.

Every month, an egg develops and is released from the ovaries, and the uterine lining forms in preparation for the implantation of a fertilized egg. If implantation does not occur, the uterine lining is shed and gets periods.

What Are the Phases of the Menstrual Cycle?

The four phases of the menstrual cycle are:

Phase 1- Menstrual Phase:

This phase usually lasts for 3 to 7 days. It is the phase of menstrual periods.
When fertilization does not occur in the previous cycle, the levels of estrogen and progesterone will drop. This results in the shedding of the uterine lining, as it is no longer required to support a pregnancy.
The symptoms include abdominal cramps, bloating, breast tenderness, mood swings, irritability, low back pain, and headaches.

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Fertility (or) Ovulation Period Calculator

Phase 2 - Follicular Phase:

This phase starts from the first day of the period to the day of ovulation. It is also called the preovulatory or proliferative phase and ends up in ovulation. So this phase also includes the menstrual phase.
This phase lasts for approximately 16 days, but depending on the length of the menstrual cycle, it can be anywhere from 11 to 27 days.
Here, the hypothalamus in the brain makes the pituitary gland release follicle-stimulating hormone (FSH), which in turn stimulates the ovaries to produce around 5 to 20 follicles.
Follicles are small fluid-filled sacs that contain an immature egg each. One or sometimes two follicles mature, and the body resorbs the rest.
The maturing follicle makes the estrogen levels rise, which thickens the uterine lining for the fertilized egg (embryo) to implant and grow.
Phase 3 - Ovulation Phase:

This is the only phase in the menstrual cycle that can result in pregnancy through unprotected sexual intercourse.
As the levels of estrogen increase, the pituitary gland releases luteinizing hormone (LH), which begins this phase. The mature egg in the ovaries is released (ovulation), and it travels through the fallopian tube to the uterus.
Ovulation can be detected by symptoms like a rise in the basal body temperature and thick white vaginal discharge.
The egg can be fertilized by a sperm only for about 12 to 24 hours after ovulation, after which the egg dissolves. But, sperm can live in the female body for up to 5 days. This increases the chase for successful pregnancy if unprotected sexual intercourse before five days of ovulation.
Phase 4 - Luteal Phase:

The follicles that remain in the ovaries after the egg is released get converted into the corpus luteum. Corpus luteum releases progesterone and little estrogen.
If fertilization of the egg does not occur, corpus luteum resorbs, and the level of progesterone and estrogen will drop. This causes the lining of the uterus to shed, and menstruation.
If not pregnant in the luteal phase, women will experience premenstrual syndrome (PMS) symptoms like bloating, breast tenderness, mood swings, etc.
What Is a Safe Period?
It is when supposedly a woman has the least chance of getting pregnant. Women go through monthly changes in their bodies in the name of the menstrual cycle. A monthly cycle has two components:

1. Proliferating Phase: This is the period that begins soon after the menstrual bleeding starts.

2. Secretory Phase: This is a constant period of 14 days, which can count as 14 days before getting the next period.

By no means, it provides complete protection against pregnancy since it has been seen that the intercourse itself may trigger untimely ovulation.

Use a safe day calculator to find out the safe days in the cycle for each month.

What Is the Unsafe Period or Fertile Days?
A woman conceives if she copulates within the time of ovulation. Hence the time of ovulation is termed as an unsafe period to have sexual intercourse, if not planning for pregnancy.

How to Calculate the Time of Ovulation?

Suppose a woman has a cycle length of 30 days; the ovulation period roughly falls in the mid 10 days.
So, to avoid pregnancy, she has to better avoid unprotected sexual intercourse in this period.
The rest of the days, starting from menstruation to the 10th day and again from the 21st day up to menstruation, are the safe days or the safe period to avoid pregnancy.
How to Calculate the Safe Period?
The safe days for women are unique and can be calculated if they have a regular menstrual cycle of 28 or 30 days. In a regular menstrual cycle, ovulation happens on the 14th day if the woman has a 28-day cycle. The ovulation time can vary from the 12th day to the 19th day of the cycle. A healthy sperm can remain in the female reproductive tract for up to 5 days, so unprotected intercourse before 5 days cannot be considered safe.

It can be calculated by :

Subtracting 18 or 19 days from the menstrual cycle, the remaining days till the start of the next menstrual cycle are considered safe and can be marked in a calendar.
Avoid the fertile days - calculate the days where there is a high chance of pregnancy and it can be from day 5 to 14 of the cycle, in a woman with a 28-day cycle. Avoid sex during those days and all the other days can be considered safe.
Subtract 11 days from the longest number of days in a cycle, and count forward from the first day of the period. Mark those days in a calendar as unsafe and the remaining days can be considered safe.
Use a safe period calculator, where the days are calculated by entering the first day of the period and the number of days in a cycle.
Always remember that sperm can live up to four or five days in the woman's reproductive tract and plan the days accordingly.


Calculating the safe periods and fertile periods helps to have sexual intercourse, according to whether planning for a child or not. The safe period can be calculated if the women have a regular cycle. The safe periods can differ for each woman and should not be compared with others. If finding it difficult to calculate the safe periods, seek help from a healthcare provider.

Frequently Asked Questions

What are the safe days?
The days of the menstrual cycle, where the chances of getting pregnant are least is called the safe period.
Which days are considered to be safe for a woman after periods?
A woman is most fertile during ovulation. For a woman with 28 to 30 days menstrual cycle, ovulation takes place during the 10th to the 14th day. But there are still chances to of getting pregnant till the 21st day. So days 1 to 7 and 14 days before your periods are considered to be safe days. But there are chances you might get pregnant on these days also, so always use other birth control methods.
How to calculate safe days?
Safe days can be calculated by counting the number of days of your periods for six months continuously. With the help of the record, count the days of your longest menstrual cycle and subtract 18 days. Count that number of days from the first day of your last period, and mark it as M.
Subtract 10 days from your shortest menstrual cycle, and count that number of days from the first day of your last period and mark it as N. The days between M and N are the most fertile days, and the other days are considered as safe days.

How do I calculate my safe days if my periods are irregular?
The same method can be used for women with irregular periods also. It is better if they monitor their menstrual cycle for more than 6 months, as it will give them a clear idea about the longest and shortest menstrual cycle. They can also use other means to track ovulation by basal body temperature and monitoring your cervical mucus.
What is ovulation?
The process by which an egg (ovum) is released from the ovary is called ovulation. Fertilization can take place up to 12 to 24 hours after ovulation. This is the most fertile period in the menstrual cycle.
When does a woman ovulate?
For a woman with a 28 to 30 days cycle, ovulation takes place between days 10 and 14. However, it can happen anywhere between days 10 and 21.
How to track ovulation?
There are many ovulation predictor kits available, which help you when you are ovulating. Other methods include: - Charting your cycle after keeping track for 6 months.

- You will see a lot of cervical mucus, which is clear, stretchy, and slippery when you ovulate.

- Your basal body temperature spikes during ovulation.
Is it safe five days before and after menstruation?
Yes, these days are considered safe. As you do not ovulate five days before or after periods, the chances of pregnancy are almost nil.
Can I get pregnant 10 days after periods?
Yes, you can get pregnant. As you ovulate around the 10th or 11th day, and the sperms are viable for up to 5 days inside a woman, fertilization is possible.
Can you get pregnant during menstruation?
The chances of pregnancy during menstruation are less. As you cannot ovulate while on periods. This is true only for women with regular cycles. As sperm can live inside you for up to 5 days, and if your menstrual cycle is short, you can still get pregnant.

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